1. Field of the Invention
This invention relates to a low conductivity refractory insulation article, e.g., a thermal insulation member, having a fiber mat and, more particularly, to a thermal insulating hollow member or sleeve having a thermal insulating fiber mat on the inner surface of the sleeve. In one non-limiting embodiment of the invention, the sleeve is mounted on water-cooled pipes in work piece support structures in a heat-treating furnace to thermally insulate and protect the pipes.
2. Description of the Available Technology
A number of different furnace insulation systems are utilized in modern day furnaces to protect the metal structures contained in the furnace and to minimize heat losses of the furnace. More particularly, the metal structures in the furnace, such as skid pipes, crossover pipes, and other support members, on pusher furnaces, and moving and fixed horizontal beams on walking beam furnaces are subjected to high and cyclic temperatures, repetitive vibrations, scale buildup, and occasional damaging blows from work pieces or chunks of metal and scale. Further, the pipes are normally hollow and water-cooled, thereby making them extremely heat absorptive.
U.S. Pat. Nos. 4,182,609 and 4,189,301 each disclose presently available insulating systems. Of particular interest in the present discussion is the insulating system disclosed in U.S. Pat. No. 4,189,301, which includes a cast refractory insulating member into which is solidly embedded a reticulated metal mesh reinforcement member having a fibrous insulating material engaged within mesh loops of the reticulated metal structure. The fibrous insulating material has better heat insulating properties than the cast refractory material.
Although the insulating member of U.S. Pat. No. 4,189,301 provides better heat insulating properties than most, if not all, other available insulating systems, there are limitations. More particularly, the fibrous insulating material has to be cut into strips and threaded through the wire loops of the mesh reinforcement member. This procedure is time consuming and/or expensive, e.g., eliminating the cutting and threading steps would reduce the cost of making the insulating member. Further, the strips of the fibrous insulating material preferably completely fill the wire loops when a refractory insulating material is subsequently cast onto the reticulated metal structure. In this manner, the cast refractory material enters the wire loops, and the reinforcement member is at least partly embedded within the refractory insulating material to reinforce both the refractory and the strips of fibrous materials and creates a bond between the two materials, which imparts a high degree of strength to the entire insulating member. As can be appreciated, when the strips of the fibrous material only partially fill the wire loops, less than the maximum thickness, length, and/or width of the strips are used, thereby reducing the maximum thermal insulation benefit that can be realized by using the fibrous insulating material with the castable refractory material. Lightweight, possible refractory material has been available for some time but its conductivity was too high resulting in bum-up of the mesh regarding enforcement and further necessitating the tedious cutting and threading steps.
As can be appreciated, it would be advantageous to provide an insulating system that includes a cast refractory insulating member, a mesh reinforcement member, and a fibrous insulating material that has heat insulating properties as good as, if not better than, the presently available insulating system and does not have the limitations of the presently available insulating system.